1. Field of the Invention
This invention relates to a method of manufacturing reinforced plastic hoses and more particularly a reinforced plastic hose having an inner diameter of 3 to 50 mm and adapted to be used under an oil pressure, pneumatic pressure or the like pressure.
2. Description of the Prior Art
In manufacturing the above mentioned kind of reinforced plastic hose, it has been the common practice to reinforce a plastic tube having a flat and smooth surface with a hard steel wire by spirally winding it around the plastic tube or by weaving it into a bag-shaped braid. In such reinforcing method, the wire tends to be easily slip along the tube surface and it is difficult to bond the tube formed of polyamide, polyester or polyurethane with the wire. As a result, such conventional method of manufacturing the reinforced plastic hose has a number of drawbacks.
1. A row of wires arranged along the tube surface becomes disordered, so that it is difficult to provide a uniform wire arrangement having a given pitch.
2. The amount of displacement of the wire is large when the hose is inflated by applying internal pressure and the mutual friction between the wires induces a premature fatigue failure of the wire.
3. In the case of cutting the hose into sections, the wire end at the cut surface of the hose section becomes outwardly enlarged due to resilient restoring force thereof, so that it is difficult to mount a metal fitting on the hose section.
4. Particularly, if the hose is covered with an outer layer, it is impossible to completely remove air from the reinforcing layer or to prevent damage of the outer layer produced when, in use, water easily penetrates into the reinforcing layer, thereby frequently coating it with rust.